>>This used to be a FAQ. The floating-point coprocessor in ix86>machines is a shared resource. There is only one. Therefore,>the state of the floating-point unit needs to be saved and>restored across all context switches. Because this is expensive>in terms of CPU time used, it is not saved and restored during>system calls. This means that if you use the coprocessor in>the kernel, you may screw up somebody's mathematics,

"somebody" is the current process, is not it? What if used in kthreads?